1. Field of the Invention
The present invention relates to a CD drive, and more specifically, to a CD drive capable of preventing an optical disk from being scraped.
2. Description of the Prior Art
With the development of digital videos and high quality digital products, compact disks (CD) have insufficient capacity and have been gradually replaced by digital video disks (DVD) having much higher capacity. A typical DVD includes two sides for recording data, so that an optical drive for reading the data stored in the DVD has to be designed to avoid scraping any side of the DVD. However, it is difficult for a prior art optical drive to read the DVD without scraping it. As the prior art optical drive is not placed horizontally, an optical disk will slightly touch a clamp of the optical drive when the optical disk is loaded into or withdrawn from the optical drive, which leads to forming scratches on the optical disk. Accordingly, a surface of the optical disk will be damaged due to long-term scratching, and further, the data stored in the optical disk may be destroyed.
For overcoming the above-mentioned problems, a clamp comprising a magnet to magnetically attract an upper cover for preventing the clamp from scraping an optical disk is disclosed in U.S. Pat. No. 6,246,654. Please refer to FIG. 1. FIG. 1 is a schematic diagram illustrating a prior art CD drive 10 having a magnetic clamp. The CD drive 10 comprises an upper cover 12, a clamp 14, a disk tray 16, a turning table 18, and a motor 20. The clamp 14 is installed inside the upper cover 12 in a movable manner, while the disk tray 16 is movably installed between the clamp 14 and the turning table 18. Additionally, the motor 20 is disposed under the turning table 18 and an optical disk 22 is put on the disk tray 16. When the CD drive 10 tries to read data stored in the optical disk 22, the turning table 18 firstly pushes the optical disk 22 upward and clamps the optical disk 22 to the clamp 14 for removing the optical disk 22 from the disk tray 16. Then, the motor 20 will drive the turning table 18 to rotate and a pick-up head of the CD drive 10 can read the data stored in the optical disk 22 thereby. The clamp 14 further comprises a magnet 24 located around a center of the clamp 14, and a yoke 26 horizontally located on an upper surface of the magnet 24. Furthermore, the yoke 16 is utilized to magnetize the magnet 24 in a vertical direction, so that magnetic attracting forces produced by the magnet 24 can act in the vertical direction.
As shown in FIG. 1, when the optical disk 22 is loaded into or withdrawn from the CD drive 10, the turning table 18 moves downward. Then, the vertical magnetic attracting forces produced by the magnet 24 in the clamp 14 act between the clamp 14 and the upper cover 12 for moving the clamp 14 upward and removing the clamp 14 from the optical disk 22. Thereby, the clamp 14 is magnetically attracted to a lower surface of the upper cover 12. Under this condition, since the yoke 24 is placed horizontally on the upper surface of the magnet 24, the magnetic attracting forces acting upward from the magnet 24 are smaller than those acting downward from the magnet 24. Furthermore, because the magnet 24 attracts the upper cover 12 through an inner wall of the clamp 14, the magnetic attracting forces acting upward from the magnet 24 are further weakened. As a result, the clamp 14 is attracted to the lower surface of the upper cover 12 under relatively weak magnetic attracting forces.
When the CD drive 10 reads the optical disk 22, the turning table 18 moves upward and clamps the optical disk 22 to the clamp 14. Accordingly, the optical disk 22 is lifted above the disk tray 16. At the same time, the turning table 18 comes close to the magnet 24 in the clamp 14 so that a distance between the magnet 24 and the optical disk 22 is smaller than a distance between the magnet 24 and the upper cover 12. Consequently, the clamp 14 is attracted downward to tightly hold the optical disk 22 under the vertical magnetic attracting forces acting between the magnet 24 and the turning table 18. Furthermore, since the magnetic attracting forces acting downward from the magnet 24 are larger than those acting upward from the magnet 24, the clamp 14 can be easily separated from the upper cover 12, and the magnet 24 provides the magnetic attracting forces for the clamp 14 to clamp the optical disk 22 more strongly. In the other words, by moving the turning table 18 upward to come closer to the clamp 14 or moving the turning table 18 away from the clamp 14, operations of descending and ascending the clamp 14 under the vertical magnetic attracting forces produced by the magnet 24 can be reversibly switched from one to the other. The detailed explanation is described in U.S. Pat. No. 6,246,654 and will not be discussed herein.
As mentioned above, the magnet 24 is introduced into the clamp 14 in the prior art. When the optical disk 22 is loaded into or withdrawn from the CD drive 10, the clamp 14 attracts the upper cover 12 through use of the magnetic attracting forces produced by the magnet 24 for preventing the clamp 14 from scraping the optical disk 22. However, the magnetic attracting forces produced by the magnet 24 decrease as temperature increases. Furthermore, the clamp 14 is attracted to the upper cover 12 under relatively weak magnetic attracting forces produced by the magnet 24. When the magnetic attracting forces produced by the magnet 24 are too small to attract the clamp 14 to the upper cover 12, the optical disk 22 will be scraped by the clamp 14. In addition, other corresponding techniques can be acquired from U.S. Pat. No. 6,373,813.